MappedByteBuffer的unmap()

public void testMappedByteBuffer() {
	int length = 10485760;
	MappedByteBuffer out = null;
	RandomAccessFile ranFile = null;
	File file = null;
                FileChannel fileChannel= null;
	try {
		file = new File("d:/test.txt");
		ranFile = new RandomAccessFile(file, "rw");
                                fileChannel = ranFile.getChannel();
		out = ranFile.getChannel().map(
		fileChannel.MapMode.READ_WRITE, 0, length);
		for (int i = 0; i < length; i++)
			out.put((byte) 'x');
		System.out.println("Finished writing");
	} catch (FileNotFoundException e) {
		e.printStackTrace();
	} catch (IOException e) {
		e.printStackTrace();
	}finally{
                    fileChannel.close();
                    ranFile.close();
                    unmap(out);
                }	
                try {
		file.delete();
		System.out.println("Delete File");
                                Thread.sleep(100000);
	} catch (Exception e) {
		e.printStackTrace();
	}
}
 
public void unmap(final Object buffer) throws Exception {
       AccessController.doPrivileged(new PrivilegedAction() {
	public Object run() {
	        try {
		Method getCleanerMethod = buffer.getClass()
                                .getMethod("cleaner", new Class[0]);
	               getCleanerMethod.setAccessible(true);
	               sun.misc.Cleaner cleaner = (sun.misc.Cleaner) 
                               getCleanerMethod.invoke(buffer, new Object[0]);
	               cleaner.clean();
	          } catch (Exception e) {
	             e.printStackTrace();
	         }
                     return null;
	  }
         });
}
 

finally{
        if(out != null){
                   fileChannel.close();
                   ranFile.close();
                   out.force();
                   out = null;
                   System.gc();
      }
}